With reference to FIG. 14, VTRs comprise a rotary head cylinder 2 mounted in a predetermined inclined posture on a chassis 1, and a pair leading guide posts 4, 41 arranged at opposite sides of the cylinder 2 and reciprocatingly movable along respective guide grooves 11, 12. A magnetic tape 10 is withdrawn from a tape cassette (not shown) and wound around the cylinder 2 by the advance of the guide posts 4, 41 to provide a specified path of travel of the tape.
A supply reel support 3 and a take-up reel support 31 are arranged on the chassis 1. Also arranged on the chassis 1 along the path of travel of the tape are a fixed guide post 42, back tension post 43, fixed guide post 44, full-width erasing head 21, sound erasing head 22, sound/control head 23, fixed guide post 45, capstan 46, pinch roller 47 and withdrawing guide post 48. The capstan 46, when driven, moves the tape 10 in one direction for recording or reproduction of signals.
As shown in FIG. 11, the sound erasing head 22 and the sound/control head 23 are mounted on a base plate 51, collectively providing a magnetic head assembly 5. The assembly 5 is supported by three post members 52, 52, 52 on a support table 9.
Referring to FIGS. 11 and 12, the support table 9 is supported by a pivot 16 projecting from the chassis 1 and by bosses 14, 15 provided on the chassis 1. Two screws 91, 92 extending through the support table 9 are screwed in the respective bosses 14, 15. The support table 9 are secured to the chassis 1 by tightening up these screws 91, 92.
The magnetic tape 10 for use in the VTR described is formed with a track pattern, on which the distance from the final end of B head recording track to the position where a control signal for the track is recorded (hereinafter referred to as the "X distance") must be set at a predetermined value.
As shown in FIG. 13, the support table 9 has two holes 93, 94 for inserting the two screws 91, 92 therethrough. The holes 93, 94 are each elongated along a circular arc centered about a hole 90 for inserting the pivot 16 therethrough. To adjust the X distance, the position of the sound/control head 23 is variable by moving the support table 9 about the pivot 16 as indicated by arrows in FIG. 11.
In the step of assembling the VTR, the X distance is adjusted by loosening the two screws 91, 92 to such an extent as to give some fastening force (prefastening force) to the support table 9, then moving the support table 9 about the pivot 16 to a position where the predetermined X distance is realized, and tightening up the two screws 91, 92 to fix the support table 9 in this position.
With the fastening mechanism wherein the screws 91, 92 are used, the fastening force varies greatly with a slight difference in the state of the screws 91, 92 as tightened. If the prefastening force of the two screws 91, 92 is excessive, a great force is required to move the support table 9, presenting difficulty in adjusting the X distance. If the prefastening force of the screws 91, 92 is conversely too small, the support table 9 will shift during the adjustment of the X distance or when the screws 91, 92 are tightened up after the distance adjustment, giving rise to the problem of producing an error in the X distance. There is another problem that the adjustment takes much time since each of the two screws 92, 92 needs tightening in two steps.